Despite the advancements in the fields of microfluidics, microfabrication and the like, there remains a fundamental problem with the implementation of these technologies in achieving their full potential. Specifically, although microfluidic systems are readily applicable to high throughput, low volume, automatable chemical and biochemical analyses and syntheses, many of the advantages gained through the use of microfluidic systems are lost through the lack of interfacing systems that are capable of functioning at the horizons of these microfluidic systems. For example, one of the major advantages of these microfluidic systems is the ability to perform operations using extremely small fluid volumes, thereby requiring smaller amounts of potentially valuable reagents and/or samples. However, although a microfluidic system may be capable of operating with fluid volumes in the nanoliter range, the lack of fluid handling systems capable of delivering such volumes to these microfluidic systems renders this advantage substantially unrealized. Specifically, the user is still required to utilize reagents and/or samples in the 1 to 10 xcexcl range.
One example of a fluidic interface which addresses these problems, namely, the introduction of samples and other fluids into microfluidic analytical systems, is described in commonly assigned U.S. application Ser. No. 08/671,986, filed Jun. 28, 1996, now U.S. Pat. No. 5,779,869 and incorporated herein by reference. In brief, the described system includes an electropipettor interfaced with the channels of a microfluidic device, for electrokinetically introducing very small volumes of samples or other materials into the microfluidic device.
In addition to fluidic interfaces, microfluidic systems also require additional device: world interfaces, including an interface between the device and the detection, sensing or monitoring means that are utilized with the system. Also required are interfaces between the device and the systems that control the operation of the device, such as systems that control fluid direction and transport within the device, and/or environmental conditions present within or around the device, and the like.
Microfluidic devices previously described in the literature have generally included only crude device: world interfaces which severely limited or eliminated a substantial proportion of the promised benefits of microfluidic systems, including automatability, ease of use, low volume and high throughput, which have been the goals of these systems.
Accordingly, there exists a need in the art for improved interfaces between microfluidic devices and the ancillary systems that are utilized with these microfluidic systems, such that these microfluidic systems can realize a greater proportion of their promised benefits. The present invention provides a solution to many of these and other problems.
The present invention generally provides improved methods, apparatuses and systems for interfacing microfluidic devices with the various systems used in conjunction with these devices, such as electrical control and monitoring systems, and the like. These improved interfaces provide microfluidic systems that are easier to use, e.g., xe2x80x9cuser friendly,xe2x80x9d are more readily automatable, and as a result, have higher throughputs than previously described analytical systems.
In a first aspect, the present invention provides an electrically controlled microfluidic system which includes a microfluidic device, an electrical controller and an electrical interface array. The microfluidic device generally comprises a body structure having an interior portion and at least a first exterior surface, a plurality of intersecting microscale channels disposed in the interior portion of the body structure, and a plurality of ports disposed in the body structure, communicating the exterior surface with the interior portion. Each of the ports is in fluid communication with at least one of the plurality of intersecting channels. The electrical control system comprises a plurality of electrical leads, each of the leads being operably coupled to a power source, where the electrical control system concomitantly delivers a voltage to each of the plurality of electrical leads. The electrical interface array permits the separate and removable coupling of each of the electrical leads with each of the plurality of ports, whereupon each of the leads is in electrical communication with a fluid disposed in each of the ports. The electrical interface array often includes a cover having at least a first surface, and a plurality of electrode pins mounted thereon, the electrode pins being oriented for insertion into the plurality of ports, each of the electrode pins being electrically coupled to a separate one of the electrical leads. Optionally, the electrical interface array further comprises a base adapted for receiving the microfluidic device, wherein an edge of the cover is attached to the base by a hinge, whereby the cover is capable of being rotatably closed over the microfluidic device mounted on the base, to insert the plurality of pins into the plurality of ports. In a further alternate aspect, the body of the device is planar in structure, and the electrical interface array comprises a plurality of electrical contact pads disposed along the at least one edge of the microfluidic device, each of the electrical contact pads being electrically coupled to at least one of the plurality of ports, and each of the plurality of electrical leads is positioned to contact a separate one of the plurality of contact pads. Alternatively, the electrical leads are disposed within a slot and oriented whereby each of the electrical leads contacts a separate one of the plurality of electrical contact pads, when the portion of the bottom layer extending beyond the top layer is inserted into the slot.
In a related embodiment, the present invention provides a xe2x80x9cclam shellxe2x80x9d comprising a base having at least one edge and at least an upper surface, the upper surface being adapted for receiving a microfluidic device. The clam shell also comprises a cover having at least a lower surface and at least one edge, the edge of the cover being connected to the edge of the base by a hinge, and the lower surface having at least a first electrical interface component. A microfluidic device is mounted on the upper surface of the base, the device comprising a body structure having an exterior surface, an interior portion defining a plurality of microscale channels, and a second electrical interface component disposed on the exterior surface and providing a plurality of separate electrical connections between the second electrical interface component and a plurality of separate points in the plurality of intersecting microscale channels, the second electrical interface component being complementary to the first electrical interface component and oriented to contact the first electrical interface component when the cover is closed over the microfluidic device. The first electrical interface array component optionally comprises an array of electrical contacts mounted on the lower surface of the cover and the second electrical interface array component comprises a plurality of electrical contact pads on the exterior surface of the microfluidic device, each electrical contact pad being in electrical communication with a separate point in the plurality of intersecting microscale channels.
In still another aspect, the present invention provides a base unit having a mounting surface adapted for receiving a microfluidic device, and a first electrical interface array component, the first electrical interface array component providing a plurality of electrical contacts, each of the electrical contacts being separately coupled to a different electrical lead from an electrical controller. Also included is a microfluidic device mounted on the mounting surface, the microfluidic device comprising a body structure having an exterior surface, an interior portion defining a plurality of microscale channels, and a second electrical interface component disposed on the exterior surface and providing a plurality of separate electrical connections between the second electrical interface component and a plurality of separate points in the plurality of intersecting microscale channels, the second electrical interface component being complementary to the first electrical interface component and oriented to contact the first electrical interface component when the microfluidic device is mounted on the mounting surface.
In an additional embodiment, the present invention provides a microfluidic system which comprises a microfluidic device having a body structure with at least first and second separate channel networks disposed therein. Each of the channel networks comprises a plurality of intersecting microscale channels, a first interface component on the body structure capable of delivering energy to the first channel network, and a second interface component on the body structure capable of delivering energy to the second channel network. The system also comprises a controller, having an energy source and a first surface adapted for mounting the body structure thereon in at least first and second fixed orientations, and including at least a third interface component operably coupled to the energy source, the third interface component being capable of transmitting energy from the energy source to the first interface component when the body structure is mounted on the mounting surface in the first orientation, and from the energy source to the second interface component when the body structure is mounted on the mounting surface in the second orientation.
In similar aspect, the present invention also provides a microfluidic system which comprises a microfluidic device having a body structure with at least first and second separate channel networks disposed therein. Each channel network comprises a plurality of intersecting microscale channels, a first interface component on the body structure capable of transmitting energy to or from the first channel network, and a second interface component on the body structure capable of transmitting energy to or from the second channel network. The system also comprises a detection system, which includes an energy detector and a first surface adapted for mounting the body structure thereon in at least first and second fixed orientations, and including at least a third interface component operably coupled to the energy detector, the third interface component being capable of transmitting energy to or from the first interface component to the detector when the body structure is mounted on the mounting surface in the first orientation, and to or from the second interface component, to the detector when the body structure is mounted on the mounting surface in the second orientation.
In yet another aspect, the present invention provides a microfluidic systems as described above, but incorporating electrical circuitry, an electrical conduit or electrode, which electrode comprises a thickness less than 1400 xc3x85, and preferably between about 800 and 1400 xc3x85. The electrode also typically comprises at least a first metal component selected from the group of tungsten, palladium, ruthenium, iridium, osmium and rhodium. In addition, the electrode does not substantially degrade at a metal/fluid interface under applied current densities greater than 0.5 mA/cm2.
In another aspect, the present invention provides an interface for use with a microfluidic device. The microfluidic device has a plurality of intersecting microscale channels and a plurality of ports for receiving fluid. The interface comprises a base for receiving the microfluidic device. A structure is movable relative to the base between a first position and a second position. A plurality of electrical interface elements are affixed to the structure. The electrical interface elements are aligned so that each electrical interface element is electrically coupled to an associated port of the microfluidic device when the microfluidic device is received by the base and the structure is disposed in the first position.
Preferably, at least three electrical interface elements will be provided in the form of rigid electrodes. These electrodes can ideally extend from the structure into the fluid in the ports of the microfluidic device. The base of the structure may be coupled together using a hinge or other mechanical coupling arrangement, and the base will often fittingly receive the microfluidic device. This arrangement can be used to maintain alignment between a large number of very small ports of the microfluidic device and the electrodes of the interface, thereby allowing complex microfluidic devices to be easily removed and replaced.
In yet another aspect, the present invention provides a microfluidic device comprising a body structure having a port (for receiving fluid) and an interior portion. The interior portion defines a plurality of intersecting microscale channels. The interior portion blocks communication between the channels and the port. An electrical interface component electrically couples the fluid in the port to the channels, or to ports in fluid communication with the channels.
In yet another aspect, the invention provides a microfluidic device comprising a body structure including an upper layer and a bottom layer. The body structure has an interior portion defining first and second intersecting microscale channels. The first channel has an un-intersected terminus. The upper layer includes first and second ports therethrough. The first port is disposed at the terminus of the first channel. The interior portion blocks fluid communication between the first port and the second port. An electrically conductive film is disposed between the first and second layers. The film electrically couples a first fluid in the first port with a second fluid in the second port. These advantageous structures allow electrical potentials to be applied to a sample fluid by inserting an electrode into a fluidically isolated port containing saline or the like. The film (or other electrical conductor) need not be disposed between the layers. For example, alternative embodiments may include conductors overlaid over the upper layer (i.e., bridging between ports). Regardless, as compared to systems in which electrodes are directly inserted into each sample, the invention provides a reduced risk of cross-contamination when replacing one microfluidic device with another.
Preferably, electrodes of the interface structure will extend into ports containing an electrolyte. The electrolyte can be electrically coupled, in turn, to a sample fluid within a sample port using a thin film conductor deposited between the layers of the microfluidic body structure, typically using any of the thin film deposition techniques developed for production of integrated circuits, recording media or the like. The use of fluid to couple an electrode to the film enhances the reliability of the electrical connection and avoids damage to the film when the electrode is moved between a coupled position and a de-couple position.
In a still further aspect, the invention provides the use of an interface to connect a microfluidic device to an electrical controller. The interface has a structure that includes a plurality of fixed electrodes disposed thereon. The electrodes are operably coupled to the electrical controller. The fixed electrodes are positioned on the structure to be inserted into a plurality of ports on the microfluidic device when the structure is moved from a first position to a second position.